Prof. Scott Hubbard of Stanford University, a former NASA manager, put it into more perspective. "You say 17,000 miles, that is huge. But remember all of those satellites out there that give us our global positioning, that tell our iPhones where we are, those are at 22,000 miles, so it is going to pass between Earth and the satellites that give us Direct TV every day. That's a close shave."

And that's why Hubbard, Apollo astronaut Rusty Schweickart and space station astronaut Ed Lu have become the Asteroid Hunters -- launching their own mission to find asteroids that have a collision with our planet in their future.

"This asteroid is important because it is a wakeup call that we should be looking out there," said former astronaut Lu. "Things do hit the earth"

The last big asteroid to hit the Earth slammed into Siberia in 1908, wiping out a thousand miles of tundra. Imagine if an asteroid the size of DA14 were to hit an urban area like San Francisco or Chicago or New York.

"If a very large asteroid hit -- I am talking about something that is miles across -- it would probably create the same kind of disaster that wiped out the dinosaurs. We are not talking about ending Earth, we are not talking about ending everything, all life on earth, but I am pretty sure it would wipe out civilization, certainly civilization as we know it."

"The truth of the matter is of all the asteroids that are out there and come near the Earth and can do harm and hit the Earth, we only know one percent of them now," said Schweickart. "Ninety-nine percent of them, we don't even know where they are."

So what are the odds of being hit by an asteroid?

"I will give you an example," said Lu. "An asteroid hits the Earth in a typical person's lifetime, let's say your lifetime, with about a one in four chance. I have a coin here, if I were to flip this twice and get heads twice, that is about the same odds as us getting smacked by an asteroid"

So it's not a matter of if, but when. And that's what prompted these asteroid hunters, who run a nonprofit organization called the B612 Foundation, to propose a radical private mission – launching a telescope called Sentinel to orbit the sun and map our solar system.

"We adopted the idea of a private mission because NASA does not have currently funding to be able to do it," said Hubbard. "They have been very successful at NASA in charting the orbits of large asteroids, the kind that probably caused the dinosaurs to go extinct. But the smaller ones that still represent a problem are not being tracked. So a group of us got together and decided we could probably raise the money and build a spacecraft to do this as a private endeavor."

Sounds simple. Build a space based telescope to orbit the sun to find asteroids but this is a unique project.

"We will put a telescope in orbit around the sun," said Lu. "It will map everything that crosses the Earth's orbit. Including all of the asteroids down to the size that can do real damage if they hit the earth"

Asteroid Passes Earth; Eventually, One Won't

But what do you do when you find an asteroid targeting Earth? If you remember the movie "Armageddon," the solution was to send Bruce Willis and a team on two space shuttles to blow it up.

"People have these crazy ideas because they get their physics from Hollywood movies," said Lu. "Never get your physics from Hollywood movies. In general, you only need to change the velocity of an asteroid by a millimeter per second. That's about the speed an ant crawls."

Lu proposes sending a spacecraft that would essentially act as a tractor – nudging the asteroid off its crash course with Earth.

"All you need to do to do is run into it with a small spacecraft, or tug at it with a space tractor," said Lu. "We are not powerless to prevent this, that part is reasonably well understood, what we need to do is find out where the asteroids are and that is what we have to solve first."

"When you look at the Earth from space, especially as I did, when you fly around the planet every hour and a half, you see the whole Earth," said Schweikart, who flew on Apollo 9 in 1969. "You identify with the whole planet and you realize that this is such a precious place."

The B612 Foundation's Sentinel telescope is envisioned as a worldwide project – one which would search the solar system for years, mapping what's out there.

"Once it makes its three dimensional map of the solar system, then that map is good for about 100 years," said Lu, who spent six months on the space station in 2003. "Sentinel can go away because we will know where those things are; if we know about it we can do something about it."